How closed?
 

The more lofted the more hooked faced, right? How many degrees closed is typical. Any suggestions as to how I can accurately establish what square and open really looks like? For horizontal hinging is open based on being square to the arc (back of low point...further up plane) , or are we actually moving it to open in our grip?

Higher lofted drivers are in the main designed to help slicers out there by being closed faced at set up. Normally 1 to 2 degrees closed though some are mega 3 or 4 efforts and marketed as slice killers.

For those with uneducated hands which are opening to the plane line into and through impact by the time the face gets to the ball the closed face is going to come in "squarer" and so ball flight direction gets a hand.

One thing that is not obvious is that if you are opening the face then the loft increases as well. It is one reason you still see a lot of 10 degree drivers in slicers ands flying high as their hand action and closed face design are going to launch it higher than the stamp on the bottom of the club.